Magnetic microspheres are used in several methods, including for example, protein purification, protein immunoprecipitation, high throughput DNA isolation, poly (A) mRNA separation, cell separation and cell purification. Magnetic microspheres are also used in biomedical applications such as drug delivery (Saiyed Z, Telang S, Ramchand C. “Application of magnetic techniques in the field of drug discovery and biomedicine”. Biomagn Res Technol. 2003 Sep. 18; 1(1):2), incorporated herein by reference. Luminex MagPlex® Microspheres can be used for multiplexed protein and nucleic acid detection using the Luminex® 100/200™ and FLEXMAP 3D® instrument systems.
Magnetic Microspheres are typically composed of superparamagnetic material embedded within a plastic bead of 1-7 μm in diameter and are easily magnetized with an external magnetic field. Once the magnet is removed, the magnetic microspheres are immediately redispersed (Saiyed, et al; 2003). Due to these properties, magnetic microspheres have become a popular alternative to standard separation techniques, such as manual or automated filtration through a membrane. The MagPlex Microspheres are polystyrene beads embedded with superparamagnetic material measuring 6.4 μm in diameter. The functional carboxyl groups on the surface of the MagPlex Microspheres allow for easy coupling to an amine group such as those found in proteins and modified oligonucleotides. MagPlex Microspheres also contain an internal array of up to 3 dyes which color code the beads, thus allowing for up to 80-plex multiplexing using the Luminex 100/200 instrument or up to 500-plex multiplexing using the FLEXMAP 3D instrument.
Washing of well plates containing the magnetic microspheres has traditionally been accomplished using an automated plate washer or a handheld pipettor. In addition, manual evacuation methods can be used to evacuate liquid reagent from a well plate containing magnetic microspheres and effectively remove supernatant and unbound analytes.
Some users find automated plate washers for magnetic bead washing prohibitively expensive. In addition, a handheld pipettor can be prohibitively time-consuming. An effective manual washing procedure for magnetic bead assays using a magnetic separator is therefore desirable.